As a support for a planographic printing plate, a plate made of pure aluminum or an aluminum alloy has been so far used. As the aluminum alloy are used various aluminum alloys containing silicon, copper, manganese, magnesium, chromium, zinc, lead, bismuth, nickel, titanium, sodium or iron. Generally, an aluminum alloy rolled plate with a thickness of 0.1 to 0.5 mm according to JIS Standard A1050 or A1100 is used. Such an aluminum alloy rolled plate is surface roughened by a mechanical method, an electrochemical method, a chemical method or a combination thereof, and then anodized to obtain a support for a printing plate.
The thus obtained aluminum alloy support, which has been surface roughened, is required to have a uniformly roughened surface without unevenness, defects or streaks in a direction of rolling. The unevenness or defects are likely to cause stains on the support surface due to ink acceptance at printing. In order to remove such unevenness or defects, there have been proposed an aluminum alloy support with a specific content of Fe, Sn, In, Ga and Zn, a specific surface roughness and a specific pit size as disclosed in JP-A-58-209597, an aluminum alloy support with a specific content of Mn and Si as disclosed in JP-A-60-230951, an aluminum alloy support with a specific content of Mn and Si subjected to a specific heat treatment as disclosed in JP-A-62-80255, an aluminum alloy support with a specific content of Mg and Mn, and with a specific crystal particle width as disclosed in JP-A-62-86143, an aluminum alloy support with a specific content of Si, Fe, Mn and Cu as disclosed in JP-A-1-306288, an aluminum alloy support with a specific content of Mg, Si, and Cu as disclosed in JP-A-1-61293, and an aluminum alloy support with a specific content of Si, Fe, Cu, Ga, Ni, and Ti as disclosed in JP-A-3-177528. However, any proposal cannot sufficiently prevent occurrence of stains on the support caused due to ink acceptance.